| Message ID | 20240209-counter-align-fix-v2-1-5777ea0a2722@analog.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | [v2] counter: fix privdata alignment | expand |
On Fri, Feb 09, 2024 at 04:50:34PM +0100, Nuno Sa wrote: > Aligning to the L1 cache does not guarantee the same alignment as > kmallocing an object [1]. Furthermore, in some platforms, that > alignment is not sufficient for DMA safety (in case someone wants > to have a DMA safe buffer in privdata) [2]. > > Sometime ago, we had the same fixes in IIO. > > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/devres.c#n35 > [2]: https://lore.kernel.org/linux-iio/20220508175712.647246-2-jic23@kernel.org/ > > Fixes: c18e2760308e ("counter: Provide alternative counter registration functions") > Signed-off-by: Nuno Sa <nuno.sa@analog.com> Applied as commit b6dce0452a02, thanks! William Breathitt Gray
diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c index 09c77afb33ca..3f24481fc04a 100644 --- a/drivers/counter/counter-core.c +++ b/drivers/counter/counter-core.c @@ -31,10 +31,11 @@ struct counter_device_allochelper { struct counter_device counter; /* - * This is cache line aligned to ensure private data behaves like if it - * were kmalloced separately. + * This ensures private data behaves like if it were kmalloced + * separately. Also ensures the minimum alignment for safe DMA + * operations (which may or may not mean cache alignment). */ - unsigned long privdata[] ____cacheline_aligned; + unsigned long privdata[] __aligned(ARCH_DMA_MINALIGN); }; static void counter_device_release(struct device *dev)
Aligning to the L1 cache does not guarantee the same alignment as kmallocing an object [1]. Furthermore, in some platforms, that alignment is not sufficient for DMA safety (in case someone wants to have a DMA safe buffer in privdata) [2]. Sometime ago, we had the same fixes in IIO. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/devres.c#n35 [2]: https://lore.kernel.org/linux-iio/20220508175712.647246-2-jic23@kernel.org/ Fixes: c18e2760308e ("counter: Provide alternative counter registration functions") Signed-off-by: Nuno Sa <nuno.sa@analog.com> --- Changes in v2: * Fixed typo in commit message; * Updated the comment block above privdata. --- drivers/counter/counter-core.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- base-commit: 81e8e40ea16329914f78ca1f454d04f570540ca8 change-id: 20240209-counter-align-fix-6fb38946af7f -- Thanks! - Nuno Sá